1. Field of the Invention
The present invention concerns a method and device for measuring the phase and amplitude of ultrashort light pulses.
2. Description of the Invention
Generally speaking, it is known that measuring the amplitude and phase of ultrashort light pulses, lasting between several femtoseconds and several picroseconds, presents a large number of difficulties.
The various currently possible measuring methods are described in the following documents:                I. A. Walmsley and R. Trebino: “Measuring fast pulses with slow detectors”, Optics and Photonics News, March 1996, vol 7, No 3, p. 23        C. Dorrer and M. Joffre: “Characterisation of the spectral phase of ultrashort light pulses”, C. R. Acad. Sc. Paris, t. 2, series IV, p. 1415-1426, 2001        
These methods differ depending on whether there is a reference pulse available for measuring the phase and amplitude of the unknown short pulse.
In the case where there is no reference pulse available, so as to determine the characteristics of the optical pulse to be measured, it is necessary to use at least one non-linear response optical element. This is detailed in the document written by C. Dorrer and M. Joffre.
Amongst the methods of this latter type, these include the FROG (Frequency Resolved Optical Gating) method, the TROG (Time Resolved Optical Gating) method and the SPIDER (Spectral Phase Interferometry for Direct Electric field Reconstruction) method, these three methods being described in the following documents:                R. Trebino and D. J Kane: “Using phase retrieval to measure the intensity and phase of ultrashort pulses: Frequency Resolved Optical Gating”, J. Opt. Soc. Am., A11, p. 2429-2437, 1993 as regards the FROG method        J. L. A. Chilla and O. E Martinez: “Direct determination of the amplitude and phase of femtosecond light pulses”, Opt. Lett., 16, p. 39-41, 1991        R. G. M. P Koumans and A. Yariv: “Time resolved Optical Gating based on dispersive propagation: a new method to characterised optical pulses”, IEEE Journal of Quantum Electronics, 36, p. 137-144, 2000 as regards the TROG method        C. Iaconis and I. A. Walmsley: “Spectral Phase Interferometry for Direct Electric field Reconstruction of ultrashort optical pulses”, Opt. Lett., p. 792-794, 1998 as regards the SPIDER method.        
It has been proved that these methods of the prior art make use of optical mountings associating a sub-unit carrying out a linear optical filtering function with said non-linear response optical element. These optical mountings are generally complex and require precise optical alignments.